
\begin{tikzpicture}[scale=.8]
  \tkzDefPoints{0/0/A,3/0/B,5/0/H,5/3/P_0}
  \tkzDefLine[altitude](A,B,P_0) \tkzGetPoint{H'}
  \tkzDrawLines(A,H A,P_0)
  \tkzDrawSegments(P_0,H B,H')
  \tkzMarkRightAngles(P_0,H,A A,H',B)
  \tkzLabelLine[right,pos=1.2](A,H){$l_0$}
  \tkzDrawPoints(A,B,H,H',P_0)
  \tkzLabelPoints[below](A,B,H)
  \tkzLabelPoints[above](P_0,H')
\end{tikzpicture}
